Tire tread



17, 1943- A c. F. OFENSEND 2,327,057

TIRE TREAD Filed May 29, 1941 JEUEEZUL 577559 F 17fsnssna Patented Aug. 17, 1943 2,327,057, TIRE TREAD Chase F. banana, Akron mi raine t The B. F. Goodrichflo'mpany, New York, N.YY.', a

corporation of New York g ApplicationrllayZB, 1941,.Serial No. 395.799

commi (01. 152- 209) This invention relates to tire treads, and especiallyto the treads of 'pneumatictires. and isin part a continuation ofrmy co-pending application, Serial No. 291,531, filed August 23, 1939 .for a .Tire tread; which matured 2,264,767, December 2,, 1941.

It. has been proposed heretofore to-provide a tread composed of circumferentially extending ribs relatively narrow as compared -to their depth so that the resistance to slippage isincreased by the tilting of the ribs under the forces on the tire tread tending to cause such slippage. However, owing to the great instability thus-provided, control and ease of steering have been objectionably reduced. Upon. increasing 1 the widths' of such ..ribs the stability has been increased,- but with an accompanying loss of resistance' to slippage. Widerg'sturdy ribs are desirable for-good load support and even wear, but such ribs heretofore have been low in resistance to slippage.

The chief objects of this invention are toprovide forovercorning disadvantages in'the prior constructions, tov provide for an adequate degree of instability of the tread element for effecting a high degree of resistance to slippage under forces tending to causeslipipage, and'at the same timetoprovide tread elements having substaninto Patent .Fig. 6 isa view like Fig. 2, but showing a further modifiedtread construction.

- Fig. 7 is a sectiontaken along the line 1 1 of Fig. 6. V 1

Fig. 8 is a-view like Fig. 2, but showing. a still further modified'tread construction Fig. 9 is a section takenalong the line 9-9 of Fig. 8.

tial bodies and broad faces for ground contact and load support, to provide improved cushion ing by. the tread for increased riding comfort, and to-provide related desirable characteristics in thestiretread including quietness of operation, long andeven'wear, and attractiveness of appearance. A further-object is to provide tread elements having under-cut portions which portions extend In theattainment of the objects of the invention in the embodiment of Figs. 1 to 3, I provide a tire, indicated generally in Fig; 1; havinga tire tread comprising ribs extending predominantly across the tread, each .wide throughout a considerable portion of its depth for maintaining. a tread face of substantial area throughout an extensive period of wear and-a tread body of considerable mass forsupportingand transmitting loads, in which tread at leastsome of the grooves extend in undercut relation into the sides of the ribs well below the tread face. This construction has the advantage that effective load-transmitting bodies of the treadmaterial. are provided with Wide ground contacting faces that remain wide throughout extensive Wear, so that, under normal conditionsand under slight accelerative and de-accelerativeand side stresses on the tire, the tread has a high degree of stability and resistance to weanand, under forces tending to cause slippage of the tire on the pavement, they aresufliciently unstable by virtue of the under cut construction to permit tilting of the tread portion between grooves to a degree suflicient for more effective action of the. tread to resist such less than the full lengthof thetread elements.

A more specificobject is to provide, in tires having elements extending in other than the circuinferential direction, tread elements having stable portions and other. portions havingless stability. j

These and further objects will be apparent from the following description reference being-had to theaccompanyingdrawing, inwhich:

Fig. l is a perspective view of a tire. constructed according to and embodying the invention-. V Fig.2 is a plan view. with parts brokenaway, of a tread construction. Fig. 3 is a section taken. of Fig. 2..

Fig, 4 isa-view like Fig. 2 but showing a modified tread construction. I r

,Fig. 5 isia section taken along the line 5-5 ofFig.4..

along the line 3-4 slippage.

. Also, this undercut construction greatly increases the cushioning qualities of the tread and .tire makes it possible to maintain higher inflacomfortable softness of ride.

In some cases it is desirable in a tread con- I struction incorporating grooved portionsto terminate the undercut. portionsof the grooves in the tread short ofthe tread margins thereby providing an adequate degree of stability and preventing uneven wear atthe free margins of the tread. Also, ina tire tread construction including ribs terminating intermediate the tread margins, it is sometimes advantageous for similar grooves.

also in the longitudinal direction, to increase the effectiveness of a tread in resistance of side slippage, each rib may be formed with a jog centrally of the tread to provide rib portions I0, at one side of the tread II, II at the other side of the tread ofiset and interconnected as shown in Fig. 2, the tread elements being separated by jogged transverse grooves l2, l2. The tread elements may be further broken by shortlongitudinal extending grooves l3, l3 and l4, E4. The grooves l2, 12 separate the ribs [0, l0, and these grooves are of such cros sectional shape as to provide walls for the ribs that extend substantially radi-.

ally into the tread for a considerable distance to provide the desired mass of the rib and auniform width for a substantial depth so that as the? tread wears down its characteristics will remain' substantially the same for an extensive period- At the bottoms of the Walls of the grooves l2, [2 they extend in undercut relation into the sidewalls of the ribs. H), 10, as indicated at I5, l5, so that uponthe application ofsufficient force to the tire the ribs will tilt about their regions at the undercut portions at the bottoms of the Upon distortion by the applic'aticnof a force on a tire the ribs tilt quite easily to increase resistance to slippage through augmenting of their edge-action. Thus, the tire tread is at once desirably stable under normal conditions and at the same time has the apparently anomalous characteristic of beinghighly effective to resist slippage under strong forces tending to cause such slippage. The dotted lines in Fig. 2 indicate the preferred extent of undercutting to reduce the stability of the ribs under forces tending to cause tilting thereof.

While it is preferred to proportion the dimensions of the ribs and grooves approximately as shown in the drawing, variations may be made in the degree of undercutting and in the tread pattern and dimensions of the ribs and grooves over a considerable range according to the amount of stability or instability desired, the construction making it possible to combine load-supporting stability and slippage-resisting instability in various degrees in any tire tread comprising ribs an grooves as desired. 7

Where the grooves are extended to the side edges of the tread to facilitate drainage it is desirable that the ribs at side margins of the tread be reinforced so that uneven wear will not result at such free margins. To this end, according to the invention, the undercut portion of the groove may be terminated short of the tread margins as is shown by the dotted lines in Fig. 2 and at i50 in Fig. 3. at the tread margins have greater stiffness whil'e the central portions of the ribs possess the characteristic of reduced stability under" tilting stresses.

The invention may be applied also to a tread having long reaches of diagonally disposed ribs, for example as is shown in Figs. 4 and 5.

Here, it is desirable to terminate the undercut portion 20, 2B of the grooves'short of the tread margin as at 2!, 2i and also to terminate such undercut portion short of the ends of the bars intermediate the tread as at 22, 22 in order that the endportions of the ribs may maintain an adequate degree of stability, while at the same time the intermediate portions of the ribs have desired instability under tilting forces. I T i With reference to Fig. 6 and 7,?theinvention is applicable alsov to treads in whichthe ribs are continuous, in azigeza'gzor'sinuous rash In this manner, the ends of the ribs ion as shown 30, 30. Each rib may be undercut in accordance with the invention as is indicated by the continuous dotted lines 3|, 3|. Circumferentiallly continuous marginal ribs 32, 32 may be provided and between these ribs the sinuous ribs triangular blocks 33, 33 may be inserted. While the undercut feature hereinabove described may be incorporated in all the ribs, for the purposeof increasing stiffness at the tread margins, the undercutting may be omitted in the marginal ribs 32, 32 and in the adjacent side of the blocks 33, 33. Both sides of the sinuous ribs 3D, 30, preferably are undercut, as is also the ad face.

jacent sides of the blocks 33, 33, the undercuts terminating at 34, 34 as indicated by the broken lines in Fig. 6.

of the drawing a plurality of circumferential ribs 48, 40, 4|, 4!, 42, 42, are shown havingportions undercut, as indicated 40a, 4la, 42a. Other and alternating portions of the same ribs may be of substantially the same width for the extent of their depth to provide for load-supporting stability as at 43, 43, 44, 44 in the side ribs 40, 40 and 4|, 4!. Where desired, the ribs may be undercut continuously but varied in the depth of the undercutting, as for example as is shown in the two center ribs 42, 42 .where relatively deep undercut portions 45, 45 alternate but merge with relatively shallow undercut portions 43, 46.

Theportions having slippage-resistant instability permit a tendency to tilt and provide for more effective traction of the tread on a sur- The relatively unstable undercut. portions maybe in line laterally as between adjacent ribs or such portions may be staggered, if desired, for considerations of quietness and wear, or such portions. may be otherwise suitably disposed in relation to each other. In the embodiment of Figs.,8 and 9 the arrangement provides gradually increasing amount of undercutting, and

therefore increasing instability, toward the center of the tread from the margins thereof, although other arrangements may be provided, as

desired, I

' port the weight 'and resist over-tilting of the ribs and maintain stability of the tire, and also quiet operation and good wear are promoted.

Variations may. be made without departing from the scope of the invention as it is defined in the following claims.

I claim: i 1. A tire having a" tread comprising a plurality of tread elements of uniform width at theitread surface separated at the tread surface .by grooves of uniform width at least some of which extend in undercut relation into the sides of the elements to provide lesser width of the elements at the undercut portions thereof than at their faces, the undercut portions terminating short of the extent of such elements.

2. A, the having a tread comprising a plurality of discontinuous ribs in the face of the tread, said ribs being separated by grooves extending in undercut relation into the sides of the ribs, said undercut portions of the grooves terminating short of the ends of the ribs.

3. A tire having a tread comprising a tread element separated from an adjacent tread area at the tread surface by a groove of uniform width, said element having a relatively stable portion of substantially the same Width for the extent of its depth, and a portion having the same Width at the tread surface of the tire as said first-named portion into which the groove extends in undercut relation providing a relatively unstable portion.

4. A tire having a tread comprising a tread element separated at the tread surface from an adjacent tread area by a groove of uniform width, said element having portions into which the groove extends in undercut relation to a relatively slight extent providing relatively stable portions, and portions into which the groove also extends in undercut relation but to a relatively greater extent providing relatively unstable portions.

5. A tire having a tread comprising a plu- L; rality of circumferentially continuous ribs of uniform width at the tread surface separated at the tread surface by grooves of uniform width, portions of at least some of which grooves extend in undercut relation into the sides of the 6. A tire having a tread comprising a plurality of circumferentially continuous ribs of uniform width at the tread surface separated at the tread surface by grooves of uniform width, said ribs having relatively stable spaced-apart portions of substantially the same Width for the extent of their depth, and intervening portions into which the grooves extend in undercut relation providing relatively unstable portions.

7. A tire having a tread comprising a plurality of circumferentially continuous ribs separated at the tread surface by grooves of uniform width, said ribs having spaced-apart portions into which the grooves extend in undercut relation to a relatively slight extent providing relatively stable portions, and intervening portions into which the grooves also extend in undercut relation but to a relatively greater extent providing relatively unstable portions.

8. A tire having a tread comprising a tread A element separated at the tread surface from an adjacent tread area by a groove of uniform width, said element having a relatively stable portion and an adjacent relatively unstable portion, said relatively unstable portion being provided by an undercut relation of said groove in the side of the element throughout the portion in a manner to provide lesser width of the element at such portion than at the adjacent portion.

9. A tire having a tread as defined in claim 8 in which the groove extends in undercut relation in both said portions of the element but to a relatively greater extent in said relatively unstable portion.

CHASE F. OFENSEND. 

